In the circuit board module and the electronic device, electronic components mounted on the circuit board include a surface mounting-type electronic component and an insertion mounting-type electronic component. The surface mounting-type electronic component is mounted on a board by soldering a terminal protruding sideward from a component body to a copper foil provided on a front surface of the circuit board. The insertion mounting-type electronic component is mounted on the board by inserting a lead terminal drawn out from the component body into a penetrating hole provided in the circuit board and soldering the lead terminal.
The electronic component mounted on the circuit board emits heat when a current flows through it. In particular, a large amount of heat is generated in the electronic component in which large current flows. When the temperature of the electronic component or the circuit board excessively rises due to heat emitted by the electronic component, there is a concern that an electronic component or an electric circuit formed on the circuit board malfunctions. Accordingly, various structures for radiating heat generated in the electronic component mounted on the circuit board have been proposed.
For example, in JP-A-2016-127256, JP-A-2016-195192, JP-A-2014-063875, JP-A-H06-244303, the surface mounting-type electronic component is mounted on the front surface of the circuit board, and a metallic heat transfer body is buried in the circuit board so as to overlap the electronic component in a board thickness direction of the circuit board. Then, heat generated in the electronic component is transferred to a back surface side of the circuit board by the heat transfer body and the heat is radiated to the outside. In particular, in JP-A-2016-127256, JP-A-2016-195192, JP-A-2014-063875, a heat radiation body is provided on the back surface side of the circuit board, heat generated in the electronic components is transferred to the heat radiation body by the heat transfer body, and the heat is radiated from the heat radiation body to the outside.
In JP-A-2010-141279, a penetrating hole is formed in the circuit board and the surface mounting-type electronic component is mounted on the front surface of the circuit board so as to cover the penetrating hole. In addition, a projection portion is formed on an upper surface of the heat radiation body provided on the back surface side of the circuit board and the heat transfer body is provided on the projection portion. The projection portion of the heat radiation body and heat transfer body are inserted into the penetrating hole from the back surface side of the circuit board so that the heat transfer body is thermally connected to the electronic component. Then, heat generated in the electronic component is transferred to the heat radiation body by the heat transfer body and the heat is radiated from the heat radiation body to the outside.
Further, in FIG. 4 of JP-A-2010-141279, a plurality of through holes are formed in the circuit board, and a plurality of penetrating conductors are provided in the circuit board by embedding solder in the plurality of through holes. The surface mounting-type electronic components are mounted on the surface of the circuit board so as to be thermally connected to the plurality of penetrating conductors. Then, heat generated in the electronic component is transferred to the heat radiation body provided below the circuit board by the penetrating transfer body and the heat is radiated from the heat radiation body to the outside.
In JP-A-2015-104182, a main body portion of the surface mounting-type electronic component mounted on the back surface of the circuit board is fitted into a recessed portion of a heat sink provided on the back surface side of the circuit board to be thermally connected to the bottom surface of the recessed portion, and heat generated in the electronic component is radiated from the heat sink to the outside.
JP-A-2013-201233, JP-A-2014-027805, JP-A-2015-053385, in order to make heat generated in the electronic component such as an FET easy to radiate, the electronic component is mounted on an end portion of the circuit board. In JP-A-2013-201233, JP-A-2014-027805, JP-A-2015-053385, JP-A-2005-184883, JP-A-2008-199721, the electronic component such as a transformer, a choke coil, and an inductor are mounted so as to penetrate through a rectangular hole formed in the circuit board and the upper surface or the lower surface of the electronic component is brought into thermal contact with a metal frame or a heat radiation plate such that heat generated in the electronic component is radiated from the metal frame or the heat radiation plate to the outside. Furthermore, in JP-A-2015-053385, a refrigerant flow path is provided on a lower surface of the metal frame to improve heat radiation performance.
In JP-A-2007-312502, the electronic component such as a transformer or a reactor is mounted on the upper surface of the circuit board, a core of the electronic component is fitted to the heat sink provided on the upper surface side of the circuit board to be thermally connected to the circuit board and heat generated in the electronic component is radiated from the heat sink to the outside.
In JP-A-2005-184883, JP-A-2008-199721, JP-A-2007-312502, one end portion of the lead terminal provided in the insertion mounting-type electronic component is mounted on the circuit board in a penetrating state, and the other end portion of the lead terminal and the main body portion of the electronic component are thermally connected to a heat radiation plate or the heat sink, and the heat generated in the electronic component is radiated from the heat radiation plate or the heat sink to the outside.
In JP-A-2015-106956, the electronic component is installed on the inner bottom surface of a casing, heat radiation fins are integrally provided in a lower portion of the casing, and heat generated in the electronic component is radiated from the heat radiation fin to the outside. In addition, a blowing fan is installed at the side portion of the casing, and cooling air is blown to the heat radiation fins by the blowing fan to improve heat radiation performance.
In JP-A-2014-045529, an opening for natural air cooling is provided on a side surface of a case that houses a circuit board, and a cooling fin and a cooling fan for forced air cooling are provided in a lower portion of the case, so that heat generated in the electronic component mounted on the circuit board is radiated.